MOTM

In a filter bank like this, the Highpass is the uppermost band and the
Lowpass is the lowermost. Like saying, "And this for everything ABOVE this
point..." So you obviously want to keep the LP near band 1 and the HP near
the highest.
 
I get the impression some of you are thinking that the LP affects the left
side and the HP the right, or something. Nothing that mysterious; these are
simply the outer bands.